U.S. Pat. No. 5,282,907 issued on Feb. 1, 1994 entitled "Cast Nickel Aluminide Alloys for Structural Application", incorporated herein by reference, describes castable Ni.sub.3 Al alloys, e.g. IC-396 (Ni 16.4 Al--8 Cr--1.5 Mo--0.5 Zr--0.15 B, at. %), for structural use at elevated temperatures in hostile environments. Further study of the metallurgical and mechanical properties of those alloys described therein has indicated two disadvantages.
Firstly, although those alloys have proven to be characterized by excellent strength at temperatures up to 850.degree. C., there is a sharp decrease in strength above 850.degree. C.
The second drawback is that those alloys showed incipient melting points (IMP) between 1150-1200.degree. C. This limits the useful temperature range of the alloys below 1150.degree. C. Consequently, those alloys cannot be exposed to temperatures above 1150.degree. C. for longer than several hours.
It is desirable to improve the strength of such alloys at high temperatures in order to achieve usefulness as a high-strength composition above 1000.degree. C. It is known that the metals industry is in need of structural materials capable of tolerating temperatures as high as 1300.degree. C. For example, many heat-treatment industries currently lack tray and fixture materials to be used at high temperatures.